客户发来询盘如下：
Books Hard cover
Cover 42 x 28cm, 4x4 colors on 250g cardboard.
Core: 480 pages, 21x14cm, 4 colors in 115g matte couche.
Guard: 4pgs, 21x14cm, 4 colors in matte couché115g.
Spine: 24mm, shirk, shirk Qty 1, matte lamination, side 1, pure glue, sewn (core), fold.
有以下问题求教：
1. Guard是 指衬页么？
2. Spine 24mm 是在书脊是24mm宽么？好像200多张纸，书脊宽不止24mm
3. Shrik 是什么意思？ 书封么？